Psalm is a static analysis tool for finding errors in PHP applications, built on top of PHP Parser.

It's able to find a large number issues, but it can also be configured to only care about a small subset of those.

Read more about Psalm, try a live demo, or install it in your project by following the guide below.

Quickstart Guide

Install via Composer:

composer require --dev vimeo/psalm

Add a config:

./vendor/bin/psalm --init

Then run Psalm:

./vendor/bin/psalm

The config created above will show you all issues in your code, but will emit INFO issues (as opposed to ERROR) for certain common trivial code problems. If you want a more lenient config you can specify the level with

./vendor/bin/psalm --init [source_dir] [level]

You can also learn how to suppress certain issues.

How Psalm Works

A basic rundown of Psalm’s internals can be found in docs/how_psalm_works.md.

Acknowledgements

The engineering team @vimeo for encouragement and patience, especially @nbeliard, @erunion and @nickyr.